A Combined Experiment and Modeling Analysis of ASTM G85 WB Accelerated Corrosion Testing of Galvanically Coupled Sensitized AA5456-H116 and CDA 706 Cupronickel

AA5456-H116 undergoes accelerated localized corrosion when in a galvanic couple with cupronickel alloy C70600 during ASTM G85 Appendix 2 Wet Bottom (G85 WB) testing. Surface and subsurface damage of AA5456-H116 was investigated and quantified. These results were compared to Finite Element Modeling results investigating relative humidity (RH) and water layer (WL) thickness. The best fit between experimental results and the modeling results was found when modeling assumed that a 3,000 µm water layer was formed during the spray portion of the G85 cycle with thinner water layers present during the decreasing RH portion of the cycle, which led IGC attack that was focused in the proximity of the CDA/AA5456-H116 interface. The high-water layer thickness is likely the result of the corrosion product formation that traps additional electrolyte than would be present on a clean surface.

Carbon Nanotube Modified by (O, N, P) Atoms as Effective Catalysts for Electroreduction of Oxygen in Alkaline Media

The influence of the types and amounts of oxygen (O), nitrogen (N), and/or phosphorus (P) heteroatoms on the surface of carbon nanotubes (CNTs) on stability and catalytic activity in the oxygen reduction reaction (ORR) was investigated in alkaline media. It is shown that functionalization of CNTs leads to growth of the electrochemically active surface and to an increase in activity in the ORR. At the same time, a decrease in stability is observed after functionalization of CNTs under accelerated corrosion testing in alkaline media. These results are most significant on CNTs after functionalization in HNO3, due to the formation of a large number of structural defects. However, subsequent doping with N and/or P atoms provides a further activity increase and enhances the corrosion stability of CNTs. Thus, as shown by the studies of characteristic parameters (electrochemical active surface values (SEAS); E1/2; corrosion stability), CNTs doped with N and NP are promising catalytic systems that can be recommended for use as fuel cell cathodes. An important condition for effective doping is the synthesis of carboxyl and carbonyl oxygen-containing groups on the surface of CNTs.

Carbon Nanotube Modified by (O, N, P) Atoms as Effective Catalysts for Electroreduction of Oxygen in Alkaline Media

The influence of the type and amount of oxygen (O), nitrogen (N), and/or phosphorus (P) heteroatoms on the surface of carbon nanotube (CNT) on stability and catalytic activity in the oxygen reduction reaction (ORR) was investigated in alkaline media. It is shown that the functionalization of CNT leads to the growth of the electrochemically active surface and to an increase in the activity in ORR. At the same time, a decrease in stability is observed after the functionalization of CNT under accelerated corrosion testing in an alkaline media. These results are most significant on CNT after functionalization in HNO3 due to the formation of a large number of structural defects. However, the subsequent doping by N and / or P atoms provides a further activity increase and enhances the corrosion stability of CNT. Thus, as shown by the studies of characteristic parameters (SEAS, E1/2, corrosion stability), CNT doped with N and NP are a promising catalytic system that can be recommended for use as fuel cell cathodes. An important condition for effective doping is the synthesis of carboxyl and carbonyl oxygen containing group on the surface of CNT.